MBB 142 lec Drosophila Flashcards
The best understood of all developmental model systems
Drosophila
Drosophila hatches from the egg as a/an?
Larva
Two axes which define early Drosophila body patterning
Antero-posterior and Dorso-ventral axes
The four regions that the dorso-ventral axis of Drosophila is divided into (from ventral to dorsal)
Mesoderm, Neuroectoderm/ Ventral ectoderm, Dorsal ectoderm, Amnioserosa
What is the amnioserosa?
An extraembryonic membrane that is sloughed off during development
The region/s that the ventral ectoderm will develop into
Ventral epidermis and Neural tissue
The region/s that the dorsal ectoderm will develop into
Epithelium
The regions that the antero-posterior axis will develop into (3)
Head, Thorax, and Abdomen
Number of parasegments
14
Number of thoracic and abdominal segments
3 and 8
Distinguishing characteristics of the segments (2)
Denticles and Bristles
Specialized structure at the posterior end of the larva
Telson
Specialized structure at the anterior end of the larva
Acron
Process of change from larva to adult
Metamorphosis
Group of cells set aside in the embryo that eventually give rise to adult structures, such as the wings and legs
Imaginal discs
Does the antero-posterior axis finish developing first before development of the dorso-ventral axis begins?
No, they occur simultaneously
The early multinucleate stage in Drosophila development
Syncytial blastoderm
What is the third dimension in the development of Drosophila, and when does this dimension form?
The proximal-distal axis, which forms during gastrulation
These genes set up the body axes
Maternal genes
Those genes which are required for subsequent development of Drosophila at later developmental stages
Zygotic genes
The four main classes of zygotic genes
Gap genes, Pair-rule genes, Segment polarity genes, and Homeotic/Selector genes
Selector genes depend on which sets of zygotic genes?
Gap genes, and Pair-rule genes
Three classes of maternal genes that define the antero-posterior axis
Those that affect anterior regions, posterior regions, and the terminal regions
T/F: Maternal genes establish differences in the antero-posterior axis after fertilization
F
Mutations that, when present in the mother, do not affect her but affects her progeny
Maternal-effect mutations
T/F: Bicoid gene expression affect nanos gene expression
F, they work independently
Mutations in what maternal gene will lead to the absence of the acron and telson?
Torso
From what germ layer does the ovary of the mother derive from?
Mesoderm
Where in the unfertilized egg is bicoid mRNA localized?
Anterior end
When is bicoid mRNA translated?
At fertilization
If a normal fertilized egg has parts A, B, C, D, and E (from anterior to posterior), and a mutant bicoid fertilized egg was injected with external bicoid at site C. What will be the arrangement of parts in the injected bicoid mutant? Assume that a larva can only have 5 parts in its antero-posterior axis.
C, B, A, B, C
What is the maternal gene that encodes for a protein that relocates bicoid mRNA to the anterior end of an egg?
Exuperantia
What is the half-life of the bicoid protein?
30 minutes
T/F: For proper patterning of the antero-posterior axis, a functioning bicoid gradient is enough.
F, both ends must be specified
This group of maternal genes control the posterior development of the Drosophila body plan
Posterior group genes
The development of what structure is impeded by mutations in posterior group genes?
Abdomen
This maternal gene product localizes nanos mRNA to the posterior end of the fertilized egg
Oskar
This maternal gene product specifies the posterior germ plasm, which eventually gives rise to the germ cells of Drosophila
Oskar
Nanos is present in the unfertilized egg as what?
mRNA
What maternal gene product/s makes a morphogen gradient with its highest level at the posterior end?
Nanos and Caudal
The expression of what (specify source) is inhibited by nanos protein?
Maternal hunchback
What causes the translation of zygotic hunchback?
Bicoid
Nanos prevents the expression of maternal hunchback by binding to the complex of? (2)
Maternal hunchback mRNA and Pumilio
If a maternal hunchback mutant were to be created, but somehow nanos expression was disturbed in the process, will the egg develop to be normal still? Why?
Yes, because the only function of nanos is to suppress maternal hunchback expression
Where is caudal mRNA initially found?
Uniformly distributed in the egg
What inhibits caudal protein expression?
Bicoid
Does the development of the two terminal regions utilize separate pathways?
No, both use the same pathway
What is the receptor protein that is important in specifying the terminal regions of the egg?
Torso
What is the ligand of the torso protein?
Trunk
Before fertilization, where (specify region) is the ligand of torso bound to?
The terminal portions of the side of the vitelline envelope facing the egg
What do you call the space in between the vitelline envelope and the cell membrane?
Perivitelline space
What prevents the ligand of torso from dispersing to the non-terminal regions of the egg?
The low amount of the ligand and the fact that most of it gets bound by torso at the terminal leads to a lack of dispersal.
What is the receptor type of the torso protein?
Receptor tyrosine kinase
What secretes the spatzle protein into the vitelline space?
Follicle cells
Where is pipe mRNA transcribed in the vitelline space by follicle cells?
Ventral 1/3 of the egg
What other maternal genes, aside from pipe, are important in the processing of spatzle? (3)
Easter, Nudel, and Windbeutel
What receptor accepts a particular form of spatzle as its ligand?
Toll
What is the form of spatzle accepted by its ligand?
Fragmented form
In what regions of the egg is Toll located in the plasma membrane?
Everywhere
What is the original location of the dorsal protein?
At the cytosolic periphery of the egg
T/F: The dorsal protein acts as both a morphogen and a transcription factor.
T
The term used to describe embryos in which no ventral structures develop.
Dorsalized
What prevents the dorsal protein from prematurely entering the nuclei?
Cactus
What are the human homologs of dorsal and cactus proteins?
NF-kB, and I-kB
Give the two maternal gene products that help in the transduction of the signal by Toll to allow the entry of dorsal protein inside the nuclei of the syncytial blastoderm.
Tube and Pelle
What is the effect of the signal from the activated Toll protein that allows for nuclear dorsal protein entry?
Degradation of bound cactus protein
What is the structure in which the original stem cell (that gives rise to the oocyte and nurse cells) is contained?
Germarium
What do you call the outgrowths of the germarium containing the developing oocyte?
Egg chamber
How many times does the original stem cell divide to give rise to the oocyte as well as its nurse cells?
4 times
What allows the nurse cells to provide to the oocyte the various maternal mRNAs that it needs for development?
Cytoplasmic bridges
What cells are mainly responsible for the patterning of the developing oocyte?
Follicle cells
What secretes the vitelline envelope, as well as the chorion of the Drosophila egg?
Follicle cells
First visible sign of antero-posterior axis development in the egg
Movement of egg towards one end of the egg chamber
What facilitates the attachment of the oocyte to the follicle cells?
E-cadherin
What facilitates the inductive signal produced by the oocyte to the follicle cells it contacts?
Gurken
What family does the gurken protein belong to?
TGF-alpha family of proteins
The receptor for the gurken protein is located where?
On the follicle cells contacting the oocyte
What is the receptor for the gurken protein?
Torpedo
What is the kind of receptor for the gurken protein receptor?
Receptor tyrosine kinase
What is the response of the egg upon receiving the signal from the follicle cells due to activation of torpedo?
Reorganization of microtubules on the antero-posterior axis
Where is bicoid mRNA produced?
By the nurse cells on the anterior portion of the egg
Which occurs first, the organization of the antero-posterior axis or the dorso-ventral axis, at least in the developing oocyte?
Antero-posterior axis is first
How many times is gurken protein expression activated during the determination of the axes of the developing oocyte?
Two times, one during antero-posterior axis determination, and another time during dorso-ventral axis determination
Most of the zygotic genes encode what type of proteins?
Transcription factors
What are the different regions present in the dorso-ventral axis, and what genes are expressed in each?
Mesoderm - Twist and Snail
Between the mesoderm and the neuroectoderm - Single-minded)
Ventral ectoderm/ Neuroectoderm - Rhomboid
Dorsal ectoderm - Tolloid and Decapentaplegic
Amnioserosa - Zerknullt
The expression of what genes is activated by high amounts of dorsal protein?
Twist and Snail
What activates rhomboid gene expression? What represses it?
Low amounts of dorsal protein; Snail
Are there regions in the fertilized egg in which both twist and decapentaplegic expression is absent? Where would this region most likely be?
Yes. It would most likely be at the neuroectoderm.
What determines the ventral pattern of early embryo?
Decapentaplegic
What is the homolog of decapentaplegic?
BMP-4
When does the embryo become cellular? (in terms of the development of the dorso-ventral axis)
After the establishment of the dorsal protein gradient/ After twist and snail expression
Why is sog necessary in the determination of the dorso-ventral axis?
It is because decapentaplegic (dpp) is an autoregulator, meaning that is activates its own expression. Sog helps prevent the spread of dpp to the ventral regions by preventing its autoregulatory effect.
What are the first genes to be expressed in the antero-posterior axis?
Gap genes
T/F: Some gap genes do not code for transcription factors, and merely code for proteins that function in the stabilization of parasegmentation.
F, all gap genes code for transcription factors.
Name five examples of gap genes.
Hunchback, Knirps, Giant, Kruppel, and Tailless
T/F: The phenotype of gap gene mutants only involves the lack of certain parts of the mutant embryo.
F, gap genes are known to have effects other than the determination of the antero-posterior axis.
T/F: The multiple regions of giant expression is indicative of an aperiodic pattern of transcription.
T
Is the embryo a syncytial or cellular blastoderm at the time of gap gene expression?
The embryo is still a syncytial blastoderm.
The expression of gap genes is controlled by…
Bicoid, hunchback, as well as the expression of other gap genes
Bicoid is a member of what family of transcriptional activators?
Homeodomain family
The transposon used to artificially introduce genes in Drosophila
P-element
The enzyme responsible for the hopping of P-elements from one region of the Drosophila chromosome to another
Transposase
An exogenous protein that can be used to temporally and spatially control the expression of the inserted genes in Drosophila.
GAL4
A technique in which a gene is randomly inserted into regions in the chromosome, and leads to the temporal and spatial expression of the inserted gene depending on the promoter and enhancer regions found near the insert site.
Enhancer trap
Describe the dependence of Kruppel expression on the levels of hunchback protein.
Kruppel expression is inhibited by both high and low levels of hunchback expression.
Describe the dependence of knirps expression on the levels of hunchback and tailless.
Knirps expression is inhibited both by high levels of hunchback, as well as the presence of tailless
This is the modules from which segments derive.
Parasegments
The segments that will fuse to form the head.
C1, C2, and C3.
First visible signs of segmentation in the embryo.
The formation of transient grooves.
Each segment is made out of? (in terms of parasegments)
The anterior portion of one parasegment, and the posterior portion of the next
The parasegments are delimited by the action of what genes?
Pair-rule genes
T/F: Pair-rule gene expression, as well as gap gene expression, are both periodic in that multiple regions of expression are found in each.
F, pair-rule gene expression is periodic, while that of gap genes is aperiodic
Does the expression of pair-rule genes depend on the wave-like expression of a corresponding morphogen?
No, pair-rule gene expression depends on the combination of particular transcription factors, such as bicoid, hunchback, as well as the gap genes.
The boundaries of the second even-skipped gene is determined by…
The levels of Kruppel and giant expression
Give three examples of pair-rule genes.
Even-skipped, Hairy, and Fushi tarazu
The expression of fushi tarazu depends on…
Expression of primary pair-rule genes, such as even-skipped and hairy
The formation of the third parasegment depends on activation of even-skipped by…
Expression of bicoid and hunchback above a certain threshold level
T/F: Segment polarity genes encode for transcription factors only.
F, they encode for a diverse kind of proteins.
The segment polarity genes act in a syncytial or cellular environment?
Cellular
The expression of this gene allows for setting up cell lineage boundaries
Engrailed
What do you call a gene which confers an identity to specific regions, and so is required to be activated for extended periods of time?
Selector genes
